When I wrote my first manuscript in LaTeX, I fall in love... even when the way to write was much more obscure, painful and bizarre than as it could be today.
Personally I prefer using the WYWIWYG editors than WYSIWYG ones.
WYWIWYG:
- Emacs: It's my personal favourite, a complete editor, useful for programming, compiling, even browsing. It has different complements for LaTeX, like Auctex.
- Kile: Is the best LaTeX editor for KDE environment.
- Texmaker: For those which prefer keeping KDE and Gnome unmixed, this is the best option.
- Windows users: My personal choice would be Texniccenter, which a.f.a.i.k. hasn't Linux version (what a shame!)
WYSIWYG:
- Lyx: It's powerful, but I don't know how to use it.
- TeXmacs: It's based on Emacs, but I didn't understand it so well.
- Windows users: There is one called Scientific Workplace, this may be `synchronised' with Maple (the symbolic calculation program) so you can even compute in the sheet you are writing... but if I don't use Lyx, this one even less.
Enjoy!